1. Field of the Invention
The present invention relates to an image stabilizer which stabilizes image blurred by vibration or the like at the time of shooting; a lens device which has the image stabilizer; and an imager apparatus such as a digital still camera or video camera, incorporating the lens device.
2. Description of the Related Art
In recent years, performance of an imager apparatus such as a digital still camera and a video camera has been improved remarkably, and it became possible for anyone to easily shoot still pictures and moving pictures with high image quality and with high efficiency. Improved efficiency of such an imager apparatus owes to high performance of an imager apparatus such as a lens, a CCD, and an image processing circuit.
However, even though the lens, the CCD and the like can be made higher in performance, if camera shake or vibration is caused by photographer's hands holding a camera (imager apparatus), blurring occurs in images with high resolution and shot images are blurred. Therefore, some relatively expensive cameras are provided with an image stabilizer capable of stabilizing images blurred by camera shake and the like upon image pickup. However, cameras that require such image stabilizer are not professional-level cameras, and it is to be understood that image stabilizers are indispensable to consumer cameras for a large number of amateur photographers with less shooting experience.
Further, in general, a demand for smaller and lighter cameras (imager apparatuses) is strong and most of photographers like cameras which are light in weight and easy to carry. However, since an image stabilizer in related art is comparatively large in size, when such large image stabilizer is mounted on a camera body, the whole of the camera becomes large in size, which is against a demand for making cameras smaller in size and lighter in weight. In addition, image stabilizers in related art require a large number of components, thereby causing a problem in which a cost of cameras increases as the number of components increases.
Japanese Patent Application Publication No. H3-186823 discloses an image stabilizer of this kind in related art, for example. In this Patent Literature, there is described one relating to a vibration-prevention device provided in a camera or the like, which detects camera shakes relatively low in frequency and uses the detected results as information for the prevention of image blurring, thereby preventing image blurring. The vibration-prevention device described in this Patent Literature (hereinafter referred to as “a first related-art example”) is a vibration-prevention device for a camera, including: a correcting optical mechanism, a vibration detector and a vibration-prevention controller. The correcting optical mechanism is provided inside a lens barrel holding a lens group and deviates the optical axis of the lens group. The vibration detector detects vibration applied to the lens barrel. The vibration-prevention controller prevents vibration by driving the correcting optical mechanism based upon a signal from the above-described vibration detector. The correcting optical mechanism has: a correcting lens, a fixing frame, a first holding frame, a second holding frame, first and second coils, first and second drivers, and first and second position detectors. The fixing frame fixes the correcting lens. The first holding frame holds the fixing frame such that the fixing frame can be moved in the first direction different from the optical axis direction of the lens group. The second holding frame holds the first holding frame such that the first holding frame can be moved in the second direction different from the optical axis direction and the first direction, and is fixed to the lens barrel. The first and second coils move the first and second holding frames in the first and second directions, respectively. The first and second drivers are formed of first and second magnetic field generating members facing the first and second coils. The first and second position detectors detect the amount in which the fixing frame and the first holding frame are moved in the first and second directions. At least either the first and second magnetic field generating members or the first and second position detectors are provided in a fixed member including the second holding frame, fixed to the lens barrel.
According to the vibration-prevention device with the structure described in Japanese Patent Application Publication No. H3-186823, there can be expected such effectiveness that the vibration-prevention device responds up to high-frequency vibration without increasing the cost and requiring a large space (refer to “Effect of the Invention”).
Japanese Patent Application Publication No. 2000-258813 discloses another example of an image stabilizer in related art, for example. In this Patent Reference, there is described one relating to an image stabilizer used for optical equipment and a lens barrel using the image stabilizer. The image stabilizer described in this Patent Reference (hereinafter referred to as “a second related-art example”) is an image stabilizer which stabilizes images by moving part of a imaging lens to the inside of a surface perpendicular to an optical axis, including: a lens holding frame, a first guide, a second guide, a first driver, a second driver, and a position detector. The lens holding frame holds a correcting lens. The first guide guides the lens holding frame to move in a first direction within a surface perpendicular to the optical axis. The second guide guides the lens holding frame to move in a second direction perpendicular to the first direction. The first driver and second driver drive the lens holding frame in the first and second directions, respectively. The position detector detects the position of the correcting lens. In this image stabilizer, the first guide and the second driver, or the second guide and the first driver are arranged to partially overlap, when seen from an optical axis direction.
According to the image stabilizer with the structure described in Japanese Patent Application Publication No. 2000-258813, the following effectiveness may be obtained, for example. Specifically, the width and height of the stabilizer can be reduced by arranging a guide shaft for moving a correcting lens, and a coil or magnet for driving the correcting lens such that a pitch moving mechanism and a yaw driver, or a yaw moving mechanism and a pitch driver are arranged to overlap when seen from an optical axis direction (see paragraph [0032]).
However, regarding the aforementioned first and second related-art examples, a holding frame which has a correcting lens is guided and supported in a movable manner in a first direction and second direction perpendicular to each other, and the first and second directions are set to be the same as the directions in which the correcting lens is moved by first and second drivers. Hence, there has been a problem that the whole of an image stabilizer becomes large and it may be difficult to be small-sized.
Such problem will be explained in detail using FIGS. 19A and 19B. FIGS. 19A and 19B schematically show the moving range of a correcting lens in a first direction X and in a second direction Y perpendicular to each other. In FIG. 19A, regarding the two axes perpendicular to each other, the first direction X is plotted on the horizontal axis and the second direction Y is plotted on the vertical axis. With those X and Y axes being reference axes, moving range in the rightward and upward directions thereof is designated as the positive (+) and moving range in the leftward and downward directions thereof is designated as the negative (−). A quadrilateral CL shown with a broken line represents a correcting lens being in focus without an image blur. With the position of this correcting lens being a reference, a correctable region M is set on the left and right sides (the rightward direction being positive and the leftward direction being negative) in the first direction X (the total correctable region is 2M), and a correctable region M is set on the upper and lower sides (the upward direction being positive and the downward direction being negative) in the second direction Y (the total correctable region is 2M).
The total correctable region 2M is obtained by adding a modification value calculated by considering dispersion of dimensions of mechanical components or the like to a reference value that is the correction range of the correcting lens necessary to correct an image blur generated. For example, if a correction amount is shown with an inclination angle in the direction of an optical axis, the correction angle equals to ±0.5°. Accordingly, as shown in FIG. 19B, the correction lens is capable of moving on the +side by a maximum range M and on the −side by a maximum distance M in the X-axis direction being the first direction X. Similarly, also in the Y-axis direction being the second direction Y, the correction lens is capable of moving on the +side by a maximum range M and on the −side by a maximum range M. Note that a moving range in the X-axis direction and a moving range in the Y-axis direction may not be equal.
Upon considering a cylindrical barrel in which a correcting lens with such correctable region is stored, an internal diameter necessary for the barrel may be the size of a length D that is the length of the correcting lens in the diagonal direction. On this occasion, moving range of the correcting lens in the X-axis direction or Y-axis direction has one to one relationship with an output from a first driver or second driver. Specifically, if the first driver outputs a driving force of 1, the correcting lens moves in the X-axis direction by a distance of M corresponding to the output of 1. Similarly, if the second driver outputs a driving force of 1, the correcting lens moves in the Y-axis direction by a distance of M corresponding to the output of 1.
In this regard, if the first driver and second driver are operated simultaneously, the correcting lens moves by a distance √2M in a direction of the resultant force obtained by combining vectors in the X-axis direction and in the Y-axis direction, in other words, moves in an oblique direction at an angle of 45° that is a diagonal direction bisecting an angle (90°) made by the X axis and Y axis. As a result, the moving range of the correcting lens is made large, causing an image stabilizer to be prevented from being small-sized.